The win32 api is a set of dll's that windows (and programs written for windows) uses. You can also use them in your vb programs. A lot of them are documented. http://www.vbapi.com http://www.allapi.net
If you want some example programs that use the api:http://vb-world.net/api/
If you have a question or problem with the api, post it in the api forum.